Color diffusion transfer process, element and composition therefor



United States Patent 3,173,786 COLOR DIFYUSIGN TRANSFER PROCESS, ELE-MENT AND COM'PGSITIQN THEREFOR Milton Green, Newton Highlands, andHoward GJRogers,

Weston, Mass., assignors toPolaroid Corporation, Cambridge, Mass, acorporation of Delaware No Drawing. Filed Aug. 22, 1960,Scr. No. 56,851

.31 Claims. (Cl. 9-6-3) The present invention is concerned withphotography and, more particularly, with color diifusion-transferprocessess.

One object of the present invention is to provide processes forimproving the density of transfer images which are produced bydiffusion-transfer processes utilizing dye developers.

Another object of the invention is to provide processes for improvingthe color separation and highlights of multicolor transfer imagesproduced by difiusiontransfer processes utilizing dye developers.

The invention accordingly comprises the several steps and the relationand order of one or more of such steps with respect to each of theothers, and the product possessing the features, properties and therelation of elements which are exemplified in the following detaileddisclosure, and the scope for the application of which will be indicatedin the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description.

The copending application of Howard G. Rogers, Serial No. 748,421, filedJuly 14-, 1958, now US. Patent No. 2,983,606, issued May 9, 1961, whichis a continuationin-part of U.S. application, Serial No. 415,073, filedMarch 9, 1954 (now abandoned); discloses and claims processes whereindye developers (i.e., dyes which contain in the same molecule a silverhalide developing function and the chromophoric system of a dye) areused to form color-transfer images. In such processes, a photosensitiveelement is exposed to create therein a latent image. The latent image isdeveloped in the presence of a dye developer; and an imagewisedistribution of unrcacted dye developer, from which the postive imagemay be created, is formed. At least a portion of the unreaoted dyedeveloper is transferred to a superposed image-receiving layer to createthereon a positive image.

in a useful mode of carrying out processes of this type, aphotosensitive element containing a silver halide emulsion is exposedand wetted by a liquid processing composition, for example, byimmersing, coating, spraying, flowing, etc., in the dark and the exposedphotosensitive element is superposed prior to, during, or after Wetting,on a sheetlike support element which may be utilized as animage-receiving element. In a preferred embodiment, the photosensitiveelement contains a layer of dye developer and the liquid processingcomposition is applied to the photosensitive element in a uniform layeras the photosensitive element is brought into superposed relationshipwith an image-receiving element. It is also contemplated to utilize thedye developer in the liquid processing composition where monochromaticimages are desired. The liquid processing composition permeates theemulsion to initiate development of the latent image contained therein.The dye developer is immobilized or precipitated in exposed areas as aconsequence of the development of the latent image. This immobilizationi apparently, at least in part, due to a decrease in the solubility ofthe dye developer upon oxidation. In unexposed and partially exposedareas of the emulsion, the dye developer is at least partly unreacted,and thus provides an imagewise distribution of unoxidized dye developer,dissolved in the liquid processing composition,

3,173,786 Patented 'Mar. 16, 1965 as a function of the point-to-pointdegree of exposure of the silver halide emulsion. At least :part of thisimagewise distribution of unoxidized dye developer is transferred, by'imbibition, to a superposed image-receiving layer or element, saidtransfer substantially excluding oxidized dye developer. Theimage-receiving element receives a depthwise diliusion from thedeveloped emulsion of unoxidized dye developer without appreciablydisturbing the imagewise distribution thereof to provide a reversed orpositive color image of the developed image.

Multicolored transfer images may be produced through various methods 'byusing at least two differentially sensitized silver halide emulsions anddeveloping each emulsion in the presence of a differently colored dyedveloper. One method comprises using integral photosensitive elementsand processes such, for example, as those claimed and disclosed in thecopending U.S. application of Edwin H. Land and Howard G. Rogers, SerialNo. 565,135, filed February 13, 1956, wherein at least two selectivelysensitized photosensitive strata are superposed on a single support andare processed with a single processing solution and transferred to acommon image-receiving layer. A suitable arrangement of this typecomprises a support carrying a red-sensitive silver halide emulsionstratum, a green-sensitive silver halide emulsion stratum, and -ablue-sensitive silver halide emulsion stratum, each of said emulsionshaving associated therewith, respectively, a cyan dye developer, nmagenta dye developer, and a yellow dye developer. In one of thepreferred embodiments of photosensitive elements used in such processes,the dye developer is disposed in a separate alkali-permeable layer,preferably behind the photosensitive silver halide emulsion with whichit is associated. The processes of the present invention are especiallyuseful in processing these integral multilayer photosensitive elements.

It has now been found that 'the density of highlights of the transferimages produced by such dye developer processes may be substantiallyimproved by carrying out the development in the presence of at least oneonium compound and especially in the presence of at least one oniumcompound selected from the group consisting of quaternary ammonium,quaternary phosphonium, and tertiary sulfonium compounds.

It is believed that such onium compounds interact with the dyedevelopers to form salts thereof and that the improvements in densityand highlights are at least due in due in part to the client of suchsalt formation on the solubility and diffusibility of the dyedevelopers.

Onium compounds have been used in the photographic art for quite sometime. For example, U.S. Patent No. 2,648,604 discloses the use ofnon-surface-aotive quaternary ammonium compounds as developmentaccelerators and U.S. Patents Nos. 2,271,623, 2,271,622 and 2,275,727disclose the use of quaternary ammonium, quaternary phosphonium andtertiary sulfonium compounds as sensitizers for silver halide emulsions.Notwithstanding the fact that such onium compounds have been previouslyused as sensitizers and as development accelerators, the results andespecially the increase in density ob tained by using onium compounds inconjunction with the dye developers in the diffusion-transfer processesof this invention are worthy of note. In the processes disclosed in theabove-mentioned U.S. patents, there is an increase in silver density inthe negative due to the use of the onium compounds; however, theincrease in density in such processes takes place in the exposed areasof the negative and is attributable to the above-mentioned ability ofthe onium compounds to sensitize an emulsion or to acceleratedevelopment. In the present processes, the increase in density which isreferred to is that which takes place in the positive image and isprimarily the result of increased transfer of the dye developer from andunexposed areas of the negative. The fact that the onium compounds wouldcoact with dye developers to increase the transfer of such dyedevelopers from unexposed areas of the negative in no way was expectedfrom the prior use made of such compoundsas sensitizers or developmentaccelerators. Further, the increase in density in the present processesis not the result of improved surface activity due to the oniumcompounds because, as will be hereinafter shown, the onium compoundswhich usually bring about the greatest improvement in density would notbe generally classified as surface active. It is believed that theincrease in density is at least due in part to the ability of the oniumcompounds to increase the solubility of the dye developers.

The fact that the onium compounds would so act with the dye developersto inhibit transfer of such developers from exposed areas and thusimproved the highlights, is similarly unexpected. This improvement inhighlights is believed to be due at least in part to the ability of theoniums, through salt formation with the dye developers, to control,especially in exposed areas, the diffusibility of such dye developers.

Especially useful results have been obtained through the use ofquaternary ammonium compounds. As is .known, quaternary ammoniumcompounds are organic compounds containing a pentavalent nitrogen atom.Generally they can be considered as derivatives of ammonium compoundswherein the four valences usually occupied by the hydrogen atoms areoccupied by organic radicals.

wherein each of the four valences is attached to separate organicradicals, e.g., tetraalkyl quaternary ammonium compounds.As'illustrations of quaternary ammonium compounds, mention may be madeof those represented by the following formulae:

wherein each R is an organic radical, Y is an anion, e.g.,

'hydroxy, bromide, chloride, toluene sulfonate, etc., and

wherein each R is an organic radical, e.g., alkyl, aralkyl, aryl, etc.groups, and X is an anion, e.g., hydroxy, bromide, chloride, toluenesulfonate, etc. As examples of tertiary sulfonium and quaternaryphosphonium compounds, mention may be made of lauryldimethylsulfoniump-toluene sulfonate, nonyl-dimethylsulfonium ptoluene sulfonate andoctyldimethylsulfonium p-toluene sulfonate, butyldimethylsulfoniumbromide, triethylsulfonium bromide, tetraethylphosphonium bromide.

The onium compounds may be used as the free base or as the salt. Whenthe onium compounds are used as the salt, the anion may be a derivativeof any acid. However, it should be noted that when the anion is iodide,such iodide may have deleterious effects on the emulsion and suitableprecautions should be taken. Especially good results were obtained whenthe onium compounds were employed as the bromide. When using oniumcompounds, which have an anion other than bromide, it has been foundadvantageous in certain instances to add a small amount of potassiumbromide.

Generally, the effect of the onium compounds on the density andhighlights will vary with the molecular size of the particular oniumcation employed. Usually the increase in density will be especiallymarked as the molecular size of the onium cation decreases. Conversely,the cleanness of the highlights will be especially noticeable withincreasing molecular size. Onium cations of intermediate molecular sizemay provide an especially marked improvement in both the density andhighlights. Generally, the cation of the onium compounds which willespecially promote increased density, will be devoid of hydrophobicchains having, for example, more than 3 carbon atoms. As examples ofsuch low molecular size onium compounds, mention may be made of:l-ethylpyridinium p-toluene sulfonate, l-propyl-pyridinium p-toluenesulfonate, N-phenyl-N,N,N-trimethylammonium p-toluene sulfonate,l-propylpyridinium bromide, 1-ethyl-2- methylpyridinium bromide,l-(fi-hydroxyethyl)-pyridinium bromide, 1-ethyl-2,3-dimethylpyridiniump-toluene sulfonate, 1-ethy1-Z-methoxypyridinium bromide,tetraethylammonium bromide, dimethyldiethylammonium ptoluene sulfonate,1,1-diethylpiperidinium bromide, l-ethyl pyridazinium methosulfate,ethyldimethylsulfonium bromide, methyl-diethylsulfonium p-toluenesulfonate, trimethylsulfonium bromide, tetramethylphosphonium bromide,ethyltrimethylphosphonium bromide, diethyldimethylphosphonium p-toluenesulfonate and propyltrimethylphosphonium bromide.

The cation of oniums which will especially promote improved highlightsgenerally will include a hydrophobic chain comprising at least, forexample, 4 carbon atoms. In a preferred embodiment the hydrophobic chainwill comprise between 4 and 16 carbon atoms and, more preferably,between about 4 and about 10 carbon atoms. As examples of suchhydrophobic chains, mention may be made of pentyl, octyl, nonyl decyl,etc., groups. The hydrophobic chain is preferably substituted directlyon the nitrogen, sulfur, or phosphorous atoms. However, in certaininstances such, for example, as in heterocyclic quaternary ammoniumcompounds, it may be present else- Where in the molecule, e.g., on theheterocyclic ring. The upper limit on the molecular Weight and length ofthe hydrophobic chain in such onium compounds is preferably determinedby the solubility and mobility of the complex of such compounds and thedye developers in the aqueous alkaline processing solution. As examplesof onium compounds containing a hydrophobic chain, mention may be madeof I-octyLZ-methylpyridinium p-toluene sulfonate, octyltrimethylammoniumbromide, lauryltrimethylammonium bromide, l-octyl-l-methylpiperidiniummethosulfate, octyltrimethylphosphonium bromide, andoctyldimethylsulfonium p-toluene sulfonate.

Hydrophobic substituents which have been found particularly useful inthe onium compounds of this invention are the aralkyls .and especiallythe phenalkyls. Onium compounds containing such substituents have beenfound especially useful in producing a marked improvement in both thedensity and the highlights. Particularly good results are obtained whenthe phenalkyl substituents are selected from those wherein the alkylportion of the molecule comprises 1 to 4 carbon atoms, e.g., benzyl,phenethyl, phenylpropyl and phenylbutyl radicals.

A class of onium compounds which has been found especially useful arethose which contain a reactive methyl group, Le, a methyl group which inallrali is capable of forming a methylene base. Such compounds, inaddition to improving the density of highlights, also provide improvedcolor separation, i.e., the transfer of the dye de velopers is moreclosely controlled by the silver halide emulsion with which each isassociated. Pyridiniurri quaternary ammonium compounds having a methylsubstituent in the 2. or 4 positions of the heterocyclic ring have beenfound especially useful as such onium compounds possessing a reactivemethyl group. The preerred 2 and 4 methyl-substituted pyridiniumcompounds are those wherein the nitrogen atoms is substituted by aphenalkyl group and especially by a phenalkyl in which the alkyl portionof the molecule comprises 1 to 4 carbon atoms. Preferred compoundsWithin this group are l-(fi-phenethyl)-2-methylpyridiniurn bromide and1- benzyl-2-methylpyridinium bromide.

In one embodiment of this invention a combination of onium compounds isemployed. Through the use of such a combination, one may strike adesired balance between the increase in density and the improvement inthe highlights. One such combination comprises using an onium compoundof small molecular "size such, for example, as those mentioned above,which are devoid of hydrophobic chains comprising more than 3 carbonatoms, with an onium compound containing a hydrophobic chain of at least4 carbon atoms. One of the pre ferred combinations comprises using anonium compound of small molecular size with a large onium compound suchas mentioned above which also contains a reactive methyl group. Such acombination is particularly eifective in producing transfer imageshaving increased density and improved highlights and color separation.In an especially useful combination, the onium compound possessing theactive methyl group is substituted by a phenalkyl group. As an exampleof such an especially use ful combination, mention may be made of theuse of N-ethylpyridinium bromide in combination with N-([iphenethyl)-2-methylpyridinium bromide. In a further modification of thepreferred combination, a higher molecular weight onium compound, e.g.,lauryl-trimethylammonium bromide is also used in the combination. Theuse of such higher molecular weight onium compounds further improves thehighlights of the transfer image.

Generally, the ability of the onium compounds to improve the colorseparation and highlights will be proportional .to the ease with whichsuch onium compounds are adsorbed on the silver halide grains of thelight- I sensitive emulsions.

In certain instances, it may be desirable to use, in conjunction withthe onium compounds, an aqueous alkaline processing solution whichincludes in part at least one organic, water-miscible solvent. Asexamples of solvents which have been found useful in this embodiment,mention may be made of dioxane, N,N-dimethy1 ethanolamine, N,N-diethylethanolamine, tetrahydrofuran, and diethylaminopropanediol. Processingsolutions comprising about of the organic, water-miscible solvent havebeen employed; however, it should be understood that this percentage maybe varied to suit particular needs.

In the abovementioned copending US. application Serial No. 748,421, itis disclosed that the density, color separation and highlights oftransfer images, which are produced in dye developer processes, may besubstantially improved by carrying out the process in the presence of atleast one silver halide developer in addition to the dye developers. Thepresent invention provides another method of bringing about theseimprovements which does not necessitate the use of such silver halidedevelopers. In a further embodiment of this invention, additionalimprovement may be made in the transfer images by using at least oneonium compound in combination with at least one silver halide developer.As examples of combinations of onium compounds and silver halidedevelopers which have been found especially useful in the processes ofthis invention, mention may be made of the use ofI-(B-phenethyl)-2-methylpyridinium bromide with trimethylhydroquinoneand the use of l-(B-phenethyl)-2-methylpyridiniuni p-toluene sulfonatewith 4'- methylphenylhydroquinone.

In carrying out the processes of this invention, there is no necessitythat the onium compounds be present in the photosensitive element at thetime of exposure. As a result of this, the onium compounds may beintroduced into the processes by various methods. In one embodiment,which has been found especially useful, the onium compounds areincorporated directly into the processing solution and inbibed into thephotosensitive element along with the other reagents used. In anotherembodiment, the onium compounds are disposed in the imagereceivingelement and during processing they are solubilized therefrom andtransferred to the photosensitive element so as to be present duringdevelopment. In still another embodiment, the onium compounds aredisposed in the photosensitive element, e.g., in special reagent layers,in the dye developer layers, etc. When using the latter embodiment, careshould be taken to prevent the onium compounds from desensitizing theemul- 510115.

In carrying out the processes of this invention, the amount of oniumcompounds used may be varied to suit particular needs. Generally, goodresults have been obtained by using processing solutions comprisingabout 1 to 10% of the onium compounds and especially good results havebeen obtained by using processing solutions comprising 2 to 4% of suchcompounds.

The previously mentioned improvements in density were especially markedin processes wherein an antifoggant was used in combination with theonium compounds. Such antifoggants tend to offset the fogging which mayoccur as an effect of the onium compounds ability to acceleratedevelopment. As examples of antifoggants which have been found useful,mention may be made of thioacetanilide, S-methylbenzimidazole,S-nitrobenzimidazole, 2 aminobenzimidazole and 1 phenyl 5-mercaptotetrazole.

The following non-limiting examples illustrate processes within thescope of the present invention:

Example 1 A photosensitive element was prepared by coating 2.gelatin-subcoated cellulose acetate film support with the followingcoating solutions:

(1) A te-trahydrofuranacetone solution (1 to l by volume) comprising5.5% of 1,4-bis-[,3-(2',5-dihydroxyphenyl)-isopropylamino]-anthraquinone(a cyan dye deveolper), about 0.8% of Resofiex 296 (trade name ofCambridge Industries (10., Inc., Cambridge, Mass, for an alkyd resinousplasticizer) and 2% cellulose acetate hydrogen phthalate.

(2) A red-sensitive silver halide emulsion.

(3) An acetone solution comprising 2% cellulose acetate hydrogenphthalate, 0.75% cellulose acetate and 0.05% S-nitrobenzimidazolc.

(4) A 2% aqueous polyvinyl alcohol solution.

(5) A 'tetrahydrofuran-acetone solution (1 to l by volume) comprising3.5% of2-'[p-(2',5'-dihydroxyphenethyD-phenylazo]-4-n-propoXy-l-naphthol (amagenta dye developer), 2% of cellulose acetate hydrogen phthalate and0.4% of Resofiex 296.

(6) A green-sensitive silver halide emulsion.

(7) An acetone solution comprising 2% cellulose acetate hydrogenphthalatc, 0.5% cellulose acetate and 0.04% 5-nitrobenzimidazole (8) A2% aqueous polyvinyl alcohol solution.

(9) A tetrahydrofuran solution comprising 3% oflphenyl-3-N-n-hexyl-carbamyl 4 [p-(2,5-dihydroxyphenethyD-phenylazo]-5-pyrazolone (a yellow dye deoxymethylpolyhexamethylene adipamide.

veloper), 2% of cellulose acetate hydrogen phthalate and 0.4% Resoflex296.

' (10) Ablue-sensitive'silver halide emulsion.

The above photosensitive element was exposed and then processed byspreading an aqueous processing solution comprising I Percent1-phenyl-3-pyrazolidone 1.2 2,5-bis-ethyleniminohydroquinone 0.9

S-nitrobenzhnidazole 0.125

l-ethylpyridinium bromide 2.5 Sodium carboxymethyl cellulose 3.0 Sodiumhydroxide 3.0

Example 2 A photosensitive element was prepared, exposed and processedin a manner similar to that employed in Example 1 except that an aqueousprocessing solution comprising:

Percent l-ethylpyridinium p-toluene sulfonate 3.0 -nitrobenzimidazole0.12

Sodium hydroxide 3.0 Sodium carboxymethyl cellulose 5.0

was employed.

Example 3 A photosensitive element was prepared, exposed and processedin a manner similar to that employed in Example 1 except that an aqueousprocessing solution comprising:

Percent Sodium carboxymethyl cellulose 5.25 Sodium hydroxide 4.0

1-butylpyridinium p-toluene sulfonate 5.0

was employed.

Example 4 A photosensitive element was prepared and processed in amanner similar to that employed in Example 1 except that an aqueousprocessing solution comprising:

Percent Sodium hydroxide 3.0 Sodium carboxymethyl cellulose 5.01,1-ethylenebis-(pyridinium bromide) 5.0

was employed.

Example 5 A photosensitive element was prepared and processed in amanner similar to that employed in Example 1 except that an aqueousprocessing solution comprising:

Example 6 A photosensitive element was prepared and processed in amanner similar to that employed in Example 1 except that an aqueousprocessing solution comprising:

Percent Sodium hydroxide 3.0 Sodium carboxymethyl cellulose 5.01,2,G-trimethylquinolinium p-toluene sulfonate 5.0 S-nitrobenzimidazole1.0 was employed. a

8 Example 7 An aqueous processing solution comprising:

Percent Sodium hydroxide 4.0 Sodium carboxymethyl cellulose 3.0/3-Hydroxyethyl-trirnethylammonium chloride 8.0 l-(fi-phenethyl)2-rnethylpyridinium bromide 5.0 S-methylbenzimidazole 0.5

was used to process an exposed photosensitive element such as employedin Example 1.

Example 8 An aqueous processing solution comprising:

Percent Sodium hydroxide 4.0 Sodium carboxymethyl cellulose 3.0l-ethylpyridinium bromide 8.0 l-(B-phenethyl)-2-methylpyridinium bromide5.0 S-methylbenzimidazole 0.5

was used to process an exposed photosensitive element similar to thatemployed in Example 1.

Example 9 An aqueous processing solution comprising:

Percent Sodium hydroxide 4.0 Sodium carboxymethyl cellulose 3.0l-ethylpyridinium bromide 8.0 l-(fi-phenethyl)-2-methylpyridiniumbromide 5.0 Cetyl-trimethylammonium bromide 2.0 S-methylbenzimidazo-le0.5 Sodium thiosulfate 1.0

was used to process an exposed photosensitive element prepared in amanner similar to that employed in Example l.

The following examples utilize a photosensitive element prepared in amanner similar to that disclosed above except that (a) the dyedevelopers were dissolved in a Waterimmiscible solvent and dispersed ingelatin rather than placed in a cellulose acetate hydrogen phthalatelayer; (b) a single gelatin interlayer Was used in place of thepolyvinyl alcohol and cellulose acetate hydrogen phthalatecelluloseacetate layer; and (c) the outer blue-sensitive emulsion was overcoatedwith a thin gelatin layer comprising about 15 mg. per square foot of4-methylphenylhydroquinone.

Example 10 n An all gelatin photosensitive element similar to thatdescribed above was exposed and processed by spreading an aqueousprocessing composition comprising:

Water cc Sodium carboxymethyl cellulose gms 4.8 Sodium hydroxide gms 4.81-( ,B-phenethyl)-2-methylpyridinium bromide gms-.. 2.4S-nitrobenzimidazole gm 0.24 Hexamethylenetetramine gms- 6.0

Example 11 A processing solution comprising:

Water cc 100 Sodium hydroxide gms 4.0 Sodium carboxymethyl cellulose gms2.5 l-ethylpyridinium bromide gms 5.0 l- (fi-phen ethyl-2-methylpyridinium bromide gms 4.0 5-nitrobenzimidazole gm 0.5Tetrahydrofuran cc 10.0

was used to process an exposed photosensitive element in a mannersimilar to that employed in Example 10.

Example 12 A photosensitive element similar to that employed in Examplewas processed in a manner similar to that employed in Example 10 exceptusing a processing solution comprising:

Example 14 The process of Example 10 was repeated except that an aqueousprocessing solution comprising:

Percent Sodium hydroxide 4.0 Sodium carboxymethyl cellulose 4.0Tetrahydrofuran 10.0 Cetyl-dimethyl-benzylammonium bromide 1.0S-nitrobenzimidazole 0.2 Sodium thiosulfate 1.0

was used.

Example 15 The process of Example 10 was repeated except that an aqueousprocessing solution comprising:

Percent Sodium hydroxide 4.0 Sodium carboxymethyl cellulose 4.0 Sodiumthiosulfate 1.0 l-(B-phenethyl)-2-methylpyridinium p-toluene sulfonate2.0 1-(B-phenethyl)-3-methylpyridinium bromide 2.0 S-nitrobenzimidazole0.2 Hexamethylenetetramine 5.0

was used.

Example 16 The process of Example 10 was repeated except that an aqueousprocessing solution comprising:

Percent Sodium hydroxide 4.0

Sodium carboxymethyl cellulose 4.0

Sodium thiosulfate 1.0 1ethyl-2,4,6-trimethylpyridinium p-toluenesulfonate 2.0

Hexamethylenetetramine 5.0

was used.

Example 17 The process of Example 10 was carried out except that anaqueous processing solution comprising:

Percent Sodium hydroxide 4.0 Sodium carhoxymethyl cellulose 5.5Triphenyl-phenacyl-phosphonium chloride 4.4 S-nitrobenzimidazole 0.1Tetrahydrofuran 10.0 Hexamethyienetetramine 5.0

was used.

Example 18 The process of Example 10 was repeated except that an aqueousprocessing solution comprising the followmg:

Percent Sodium hydroxide 4.0 Sodium carboxymethyl cellulose 3.5T-riethylsulfonium tosylate 4.2 S-nitrobenzimidazole 0.5 was employed.

Each of the transfer images produced in the above examples showedsubstantial improvements over similar transfer images produced withoutthe use of the onium compounds.

It should be noted that in Example 4, the process is carried out in thepresence of a compound containing two quaternary ammonium radicals. Theterm onium compound as used herein is intended to include compoundscontaining one or more onium radicals.

As examples of additional onium compounds which have been similarlytested and found useful, mention may be made of the following:

p-Chlorophenacyl pyridinium bromideZ-methylbenzothiazole-N-B-carboxyethobromideZ-methylbcnzothiazole-N-carboxymethobromide l-benzylpyridinium bromidel-benzyl-a-picolinium bromide1,2-di-(2-[N-benzyH-pyridinium)-1,2-ethane-diol bromide l-mcthylpyridinium tosylate lnethyl u-picolinium tosylate l-methyl-y-picoliniumtosylate Carboxymethyl-triphenyl-phosphonium bromidel-rnethyl-2,6-lutidinium p-toluene sulfonate 2,3,4-trimethylthiazoletosylate Diethyl-carboxymethyl sulfoniurn bromideN-r'nethyl-Z-benzylmercaptothiazoliniurn methyl sulfate N-nethyl-Z-methylmercaptothiazoline methyl sulfate l-benzylZ-ethylpyridinium bromide l-methoxy-a-picolinium methosulfate6-methoxy-1- (fi-phenethyl -quinolinium bromide phenylene diamrnoniumbromide 1- js-phenethyl -a-picolinium perchlorate l-benzyl-4-n-propylpyridinium bromide l-ethyl-a-picolinium bromide l-methyl-a-picoliniumbromide l-n-propyl-wpicolinium bromide l-benzyl-Z-benzyl pyridiniumbromide 1-benzyl-4-benzyl pyridinium bromide l-benzyl-Z-n-amylpyridinium bromide l-benzyloxy-a-picolinium bromide 1-(p-methylbenzyl)-a-picolinium bromide l-(y-phenoxypropyl)-a-picoliniumbromide l (p-nitrobenzyl) -a-picolinium bromide 'l-laurylpyridiniump-toluene sulfonate Trimethylphenylammonium benzene sulfonate2,6-dimcthyl-1-methyl quinoliniurn toluene sulfonate l-ethylpyridiniump-toluene sulfonate 1-methyl quinoliniurn chloride N-methylquinoliniummethyl sulfate Trimethylphenylammonium hydroxide Tetrabutylammoniumbromide Tetrabutylamrnonium hydroxide Tetraethylammonium hydroxideCetyldimethylbenzylarnmonium chloride Tetra-n-propylammonium hydroxidel-methylpyridinium hydroxide N,N-dimethylpyrrolidinium hydroxide Theeffectiveness of the onium compounds in improving the density and colorseparation of the transfer images was evidenced by tests wherein areasof 3-color nega .tives such as used in Examples through 18 were exposedto (1) blue and green light only, (2) red and blue light only, and (3)red and green light only. Transfer images were prepared from onenegative by using an aqueous processing solution containing no oniumcompounds (Solution A), from a second negative by using an aqueoussolution containing the oniums (Solution B) and from a third negative byusing an aqueous process ing solution comprising both the oniums and awatermiscible solvent (Solution C). The solutions comprised thefollowing.

Solution A: Percent Sodium hydroxide 4.0 Sodium carboxymethyl cellulose3.5 S-nitrobenzimidazole 0.5

Solution B:

Sodium hydroxide 4.0 Sodium carboxymethyl cellulose 3.5l-ethylpyridinium bromide 5.0

=1-(,B-phenethyl)=2-methylpyridinium bromide 4.0

S-nitrobenzimidazole 0.5

Solution C:

Sodium hydroxide 4.0 Sodium carboxymethyl cellulose 5.5l-ethylpyridinium bromide 1.0 1- (fl-phenethyl) -2-methylpyridiniumbromide 4.0

S-nitrobenzimidazole 0.5 Tetrahydrofuran -Q 10.0

The analytical cyan, magenta and yellow densities of the resultingtransfer images were measured by reflectance. Theoretically, only cyandye developer should transfer from the negatives exposed to green andblue light, only magenta dye developer should transfer from thenegatives exposed to red and blue light and only yellow dye developershould transfer from the negatives which were exposed to green and redlight. The results obtained appear in tabular form below:

SOLUTION A SOLUTION C Density Exposure Cyan Magenta Yellow Blue andGreen -Q 1. 31 0.12 0. 13 Red and Blue 0.20 0. 65 0. 12 Red and Green0.12 0.16 1. 24

Similar tests wherein areas of the negative were exposed to blue, redand green light only, further exidenced the ability of the onium toincrease the density and color separation.

The dye developers which are used in the processes of this invention, asnoted above, are compounds which contain in the same molecule both thechromophoric system of a dye and also a silver halide developingfunction. Particularly useful results have been obtained when the oniumcompounds were. used in conjunction with dye developers comprisinghydroxy-substituted benzenoid silver halide developing radicals andespecially benzenoid silver halide radicals which are substituted by atleast two hydroxy groups, e.g., hydroquinone and catechol radicals.Representative dye developers for use in the processes of this inventionare disclosed in the previously mentioned US. application of Howard G.Rogers, Serial No. 748,421, now US. Patent No. 2,983,- 606. Additionaluseful dye developers are described in the following copending US..applications:

Application Serial No. 824,785, filed July 3, 1959, now abandoned, inthe names of Elkan R. Blout, Marilyn R. Cohler, Milton Green, Myron S.Simon and Robert B. Woodward.

Application Serial No. 612,045, filed September 25, 1956,

now abandoned, in the names of Elkan R. Blout, Milton Green andHowardG.Rogers.

Application Serial No. 612,052, filed September 25, 1956,

now abandoned, in the name of Myron S. Simon.

Application Serial No. 612,054, filed September 25, 1956, now abandoned,in the names of Helen P. Husek and Myron S. Simon.

Application Serial No. 612,055, filed September 25 1956,

now abandoned, in the name of Helen P. Husek.

Application Serial No. 755,804, filed August 18, 1958, now abandoned, inthe names of Elkan R. Blout, Saul G. Cohen, Milton Green and Myron S.Simon.

Application Serial No. 849,727, filed October 30, 1959 now abandoned, inthe names of Elkan R. Blout and Myron S. Simon.

Application Serial'No. 1,442, filed January 11, 1960, in the names ofElkan R. Blout, Saul G. Cohen, Milton Green, Howard G. Rogers, Myron S.Simon and Robert B. Woodward.

The aqueous solutions used'in the processes of this invention arealkaline in nature and preferably should have a pH of at least 12. Someexamples of alkaline materials which may be used are sodium hydroxideand potassium hydroxide, etc. In certain instances, an all quaternaryprocessing solution may be employed by using quaternary hydroxides suchas choline and tetrarnethylammonium hydroxide in place of the alkalimetal hydroxides.

- As pointed out above, in one of the preferred embodiments of thisinvention, the onium compounds are used in combination with a silverhalide developer in addition to the dye developers. The silver halidedevelopers which have been found especially useful in this embodimentare the hydroxyl-substituted aryl developers, for example,toluhydroquinone, 5,8-dihydro-1,4-naphthohydroquinone, o-

13 toluthiohydroquinone, 5,6,7,8-tetrahydro-1,4-naphthohydroquinone,methoxyhydroquinone and 2,6-dimethylhydroquinone.

As will be understood, the onium compounds for use in the processes ofthis invention will be difiusible in the alkali-permeable film-formingmaterials which are used in the emulsion and other layers of thephotosensitive element. Many alkali-permeable, film-forming materialsare available for this use and the particular materials employed willvary depending on ones particular choice. As examples of film-formingmaterials, which have been used, mention may be made of gelatin,polyvinyl alcohol and cellulose acetate hydrogen phthalate.

It will be further understood that the oniums will be preferablycolorless so as not to alter the color of the transfer image.

The coaction of the onium compounds with the dye developers wasevidenced by a dye diffusion front test wherein the initial diffusionrate of 2-[p-(2',5'-dihydroxyphenethyl -phenylazo]-4-n-propoXy-1-naphthol (magenta dye developer) through gelatin wasmeasured using a processing solution containing no quaternary ammoniumcompound and using a processing solution containingN-{S-phenethyl-a-picolinium bromide. It was found that the quaternaryammonium compound reduced the initial diffusion rate of the dyedeveloper. It is believed that this reduction in the initial difiusionrate of the dye developers tends to prevent premature transfer and thuspromotes an improvement in the highlights.

The processes of this invention are especially useful in composite filmunits intended for use in a Polaroid Land Camera, made by PolaroidCorporation, Cambridge 39, Massachusetts, or a similar camera structuresuch, for example, as the camera forming the subject matter of US.Patent No. 2,435,717, issued to Edwin H. Land on February 10, 1948. Ingeneral, such composite film units comprise a photosensitive element,such as the integral multilayer element heretofore described, animagereceiving element and a rupturable pod containing an aqueousalkaline processing solution. The photosensitive element,image-receiving element and pod are so associated with each other that,upon processing, the photosensitive element may be superposed on theimage-receiving element and the pods may be ruptured to spread theaqueous alkaline processing solution between the superposed elements.The nature and construction of the pods used in such rolls are wellknown to the art. See, for example, US. Patents Nos. 2,543,181 and2,634,886, issued to Edwin H. Land.

The processes of this invention are further suitable for use with screentype photosensitive elements such as disclosed in the aforementionedapplication of Howard G. Rogers, Serial No. 748,421, now US. Patent No.2,983,- 606, and also the copending application of Edwin E. Land, SerialNo. 448,441, filed August 9, 1954, now US. Patent No. 2,968,554, whereinat least two selectively sensitized silver halide emulsions are arrangedin the form of a screen and the color-providing substances, as inmultilayer photosensitive elements, are preferably placed in a separatealkali-permeable layer in back of the photosensitive emulsion with whichthey are associated.

The term dye developer as used herein is intended to includecolor-shifted dye developers such as those disclosed in the copendingapplication of Howard G. Rogers, Serial No. 789,080, filed January 26,1959.

Since certain changes may be made in the above processes and productswithout departing from the scope of the invention herein involved, it isintended that all matter contained in the above description shall beinterpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A process of forming a transfer image in color which comprisesexposing a photosensitive element comprising at least one silver halideemulsion, each of said silver halide emulsions having associatedtherewith a dye dei l veloper, each of said dye developers containing ahydroxysubstituted benzeuoid silver halide developing radical,developing said exposed photosensitive element, forming in undevelopedareas of each said silver halide emulsion, as a function of saiddevelopment, an imagewise distribution of said associated dye developerin unoxidized, diilusible condition, and transferring, by diffusion, atleast a portion of each said imagewise distribution of unoxidized dyedeveloper to a superposed image-receiving layer to form said colortransfer image, said process including the step of efi'ecting saiddevelopment and transfer in the presence of at least one onium compoundselected from .the group consisting of quaternary ammonium, quaternaryphosphonium and tertiary sulfonium compounds, said onium compound beingprovided by application to said photosensitive element of an aqueousalkaline processing solution containing said onium compound.

2. A process as defined in claim 1 wherein said onium compound is addedto said processing solution as the salt thereof.

3. A process as defined in claim 1 wherein said onium compound is aquaternary ammonium compound.

4. A process as defined in claim 3 wherein said quaternary ammoniumcompound is a tetraalkyl quaternary ammonium compound.

5. A process as defined in claim 3 wherein said quaternary armnoniumcompound is a heterocyclic quaternary ammonium compound.

6. A process as defined in claim 5 wherein said heterocyclic quaternaryammonium compound is a derivative of pyridine.

'7 A process as defined in claim 5 wherein said heterocyclic quaternaryammonium compound contains a phenalkyl substituent on the pentavalentnitrogen atom.

8. A process as defined in claim 7 wherein said phenalltyl substituentis a phenethyl group.

9. A process as defined in claim 7 wherein said phenallryl group is abenzyl group.

10. A process as defined in claim 1 wherein development is carried outin the presence of at least one substantially colorless silver halidedeveloping agent in addition to said dye developer.

11. A process as defined in claim 1 wherein said hydroxy-substitutedbenzenoid silver halide developing radical in said dye developer is ahydroquinoyl radical.

12. A process as defined in claim 1 wherein said aqueous alkalineprocessing solution includes a water-miscible organic solvent.

13. A process as defined in claim 1 wherein said aqueous alkalineprocessing solution has a pH of at least l2.

14. A process as defined in claim 1 wherein said development is carriedout in the presence of at least a first and a second onium compound,each of said onium compounds being selected from the group consisting ofquaternary ammonium, quaternary phosphoniurn, and tertiary sulfoniumcompounds, the cation of said first onium compound being free ofhydrophobic chains comprising more than 3 carbon atoms and the cation ofsaid second onium compound containing a hydrophobic chain of at least 4carbon atoms.

15. A process as defined in claim 14 wherein said first onium compoundis a quaternary ammonium compound and said second onium compound is aquaternary ammonium compound.

16. A process as defined in claim 1 wherein said onium compound is freeof hydrophobic chains comprising more than 3 carbon atoms.

17. A process as defined in claim 15 wherein the hydro phobic chain ofsaid second onium compound comprises from 4 to 16 carbon atoms.

18. A process as defined in claim 15 wherein the hydrophobic chain ofsaid second onium compound comprises from 4 to 10 carbon atoms.

19. A process as defined in claim 1 wherein an antifoggant is present insaid processing solution with said onium compound.

20. A process as defined in claim 1 wherein said processing compositioncontains an alkali metal hydroxide.

21. A process as defined in claim 1 wherein said onium compound ispresent in said processing solution in a concentration of about 1% to10%.

22. A process as defined in claim 1 wherein said onium compound ispresent in said processing solution in a concentration of about 2% to4%.

23. A process as defined in claim 1 wherein said onium compound iscolorless.

24. A photographic product comprising (a) a photosensitive element, saidphotosensitive el'ment comprising a support carrying at least one silverhalide emulsion, each said silver halide emulsion having associatedtherewith a dye developer, each of said dye developers containing ahydroXy-substituted benzenoid silver halide developing radical, (b) animage-receiving element comprising a support carrying an image-receivinglayer, and (c) a rupturable container releasably holding an aqueousalkaline processing solution, said aqueous alkaline processing solutionincluding an onium compound selected from the group consisting ofquaternary ammonium, quaternary phosphonium and tertiary sulfoniumcompounds, said photosensitive element and said imagereceiving elementbeing capable of being superposed on each other with said rupturablecontainerpositioned therebetween so as to release said processingsolution, upon rupture of said container, to permeate said silver halideemulsions and said image-receiving layer.

25. A photographic product as defined in claim 24, wherein saidphotosensitive element comprises a support carrying a red-sensitivesilver halide emulsion stratum, 'a green-sensitive silver halideemulsion stratum, and a blue-sensitive silver halide emulsion stratum,each of said silver halide emulsions having associated therewith,respectively, a cyan dye developer, a magenta dye developer, and ayellow dye developer, each said dye developer being disposed in analkali-permeable layer behind its associated silver halide emulsion.

26. A photographic product as defined in claim 20, wherein said oniumcompound is added to said processing solution in the form of a bromidesalt thereof.

27. A photographic developer composition comprising an aqueous alkalinesolution comprisin'gan alkali metal hydroxide, a dye developer, said dyedeveloper containing a hydroxy-substituted benzenoid silver halidedeveloping radical, and at least one colorless onium compound selectedfrom the group consisting of quaternary ammonium, quaternary phosphoniumand tertiary sulfonium compounds.

28. A photographic developer composition as defined in claim 27 whereinsaid composition includes sodium carboxymethyl cellulose.

29. A photographic developer composition as defined in claim 27 whereinsaid composition also includes a substantially colorless silver halidedeveloping agent.

30. A process of forming a'transfer image in color which comprisesexposing a photosensitive element comprising at least one silver halideemulsion, each of said silver halide emulsions having associatedtherewith a dye developer, each of said dye developers containing ahydroXy-substituted benzenoid silver halide developing radical,developing said exposed photosensitive element, forming in undevelopedareas of each said silver halide emulsion, as a function of saiddevelopment, an imagewise distribution of said associated dye developerin unoxidized, diffusible condition, and transferring, by diffusion, atleast a portion of each said imagewise distribution of unoxidized dyedeveloper to a superposed image receiving layer to form said colortransfer image, said process including the step of effecting saiddevelopment and transfer in the presence of at least one onium compoundselected from the group consisting of quaternary ammonium, quaternaryphosphonium and tertiary sulfonium compounds, said onium compound beinginitially positioned in one of (a) said photosensitive element, (12) anaqueous alkaline processing composition applied to said photosensitiveelement to efiect said development and transfer, and (c) animage-receiving element including 'said image-receiving layer, saidonium compound being transferred by diflusion from its initial locationto each said silver halide emulsion, whereby the density of said colortransfer image is increased.

31. A process as defined in claim 30 wherein said onium compound isinitially positioned in said image-receiving layer, said aqueousalkaline processing solution is applied between said image-receivingelement and said photosensitive element, and said onium compound issolubilized by said aqueous alkaline processing solution and transferredby diifusion to each said silver halide emul- SlOIl.

References Cited by the Examiner UNITED STATES PATENTS 2,197,809 4/40McQueen 9666 2,271,622 2/42 Carroll et al 96107 X 2,271,623 2/42 Carroll96--107 X 2,275,727 3/42 Carroll et al. 96107 X 2,371,740 3/45 Dearing9661 2,648,604 8/53 Welliver et al. 9655 X 2,868,077 1/59 Ryan et al.88-65 2,886,437 5/59 Piper et al. 9666 2,983,606 5/61 Rogers 96292,997,390 8/61 Land 9629 3,019,108 1/62 Dershowitz 96--29 3,034,894 5/62Jeffreys 9699 3,043,692 7/62 Haas et al. 9629 3,061,437 10/62 Burness etal. 96108 3,061,453 10/62 Rogers 11734 3,065,075 11/62 Dershowitz 96293,077,400 2/ 63 Rogers et al. 96-==-3 FOREIGN PATENTS 554,935 8/57Belgium. 221,880 5/59 Australia.

OTHER REFERENCES James et al.: JACS, 60, 2084-2093 (1938).

Mosher: American Dyestuff Reporter, Ian. 20 (1941), pp. P32-P38.

Willems: Science et Industr. Phot., 27, 487-488 (1956).

NORMAN G. TORCHIN, Primary Examiner.

PHILIP E. MANGAN, Examiner.

UNITED STATES PATENT oTTTcE CERTIFMATE 0i QQRREQTMN Patent No. 3,173,786March 16, 1965 Milton Green et ale It is hereby certified that errorappears in the above numbered patent requiring correction and that thesaid Letters Patent should read as correctedbelow.

Column 2, line 14, for "dveloper" read developer line 36, for "of" readand same column 2, line 46, strike out "due in"; column 3, line 17, for"improved" read improve column 5, line 14, for "atoms" read atom column6, lines 53 and 54, for "deveolper" read developer column 9, line 29,after "that" insert a column ll, line 25, for "following." readfollowing: column 12, line 12, for exidenced" read evidenced Signed andsealed this 26th day of Ocotber 1965!.

(SEAL) Attest:

ERNEST W, SWIDER EDWARD J. BRENNER Amzsting Qfficer Commissioner ofPatents

1. A PROCESS OF FORMING A TRANSFER IMAGE IN COLOR WHICH COMPRISESEXPOSING A PHOTOSENSITIVE ELEMENT COMPRISING AT LEAST ONE SILVER HALIDEEMULSION, EACH OF SAID SILVER HALIDE EMULSIONS HAVING ASSOCIATEDTHEREWITH A DYE DEVELOPER, EACH OF SAID DYE DEVELOPERS CONTAINING AHYDROXYSUBSTITUTED BENZENOID SILVER HALIDE DEVELOPING RADICAL,DEVELOPING SAID EXPOSED PHOTOSENSITIVE ELEMENT, FORMING IN INUNDEVELOPED AREAS OF EACH SAID SILVER HALIDE EMULSION, AS A FUNCTION OFSAID DEVELOPMENT, AN IMAGEWISE DISTRIBUTION OF SAID ASSOCIATED DYEDEVELOPER IN UNOXIDIZED, DIFFUSIBLE CONDITION, AND TRANSFERRING, BYDIFFUSION, AT LEAST A PORTION OF EACH SAID IMAGEWISE DISTRIBUTION OFUNOXIDIZED DYE DEVELOPER TO A SUPERPOSED IMAGE-RECEIVING LAYER TO FORMSAID COLOR TRANSFER IMAGE, PROCESS INCLUDING THE STEP OF EFFECTING SAIDDEVELOPING AND TRANSFER IN THE PRESENCE OF AT LEAST ONE ONIUM COMPOUNDSELECTED FROM THE GROUP CONSISTING OF QUATERNARY AMMONIUM, QUARTERNARYPHOSPHONIUM AND TERIARY SULFONIUM COMPOUNDS, SAID ONIUM COMPOUND BEINGPROVIDED BY APPLICATION TO SAID PHOTOSENSITIVE ELEMENT OF AN AQUEOUSALKALINE PROCESSING SOLUTION CONTAINING SAID ONIUM COMPOUND.